Color filter substrate and lcd utilizing the same

ABSTRACT

A color filter substrate and an LCD applying the same are provided. This color filter substrate has a plurality of color filters with overlap regions acting as black matrix. Subsequently, patterned regions are defined in part of the overlap regions. After formation of a planarization layer and a conductive layer, spacers are formed overlying the patterned regions. The spacers may not shield the transparent region of the color filters, thereby enhancing the aperture ratio of the color filter substrate. Additionally, the thickness of planarization layer in the patterned regions is not influenced by the overlap of the color filters, such that the spacers thereon have a uniform height.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a liquid crystal display (LCD), and inparticular to a color filter substrate thereof.

2. Description of the Related Art

Conventional LCD comprises a color filter substrate, an array substrate,and a liquid crystal layer disposed therebetween. Formerly, the distancebetween the substrates was defined by ball spacers. However, no methodexisted to regulate distribution thereof, so use of a patternedphotoresist layer as a spacer became popular.

Conventional large color filter substrate includes black matricesbetween different color filters, with middle or small color filtersubstrates serving in overlap regions of different color filters asblack matrices. As shown in FIGS. 1A and 1B, color filter substrateincludes red, green, and blue color filters 10R, 10G, and 10B on asubstrate 11, wherein the color filters overlap to form overlap regions12A and 12B. FIG. 1B is a section view of line X-X′ in FIG. 1A, definingthe overlap regions. The thickness of overlap regions 12A and 12B isinfluenced by overlap of two color filters. To ensure spacers haveuniform height, spacers are preferably formed beyond the overlap region.For example, the spacer 14 is formed in the corner of transparent regionof the color filter 10R in FIG. 1A. Thus, spacer 14 formed intransparent region of any color filter will reduce aperture ratio of thecolor filter. If the spacer 14 is directly formed in the overlap region12A or 12B, the overlap difference of color filters 12R, 12G, and 12Bwill result in different height of spacers 14. Thus, a method is calledfor forming uniform height spacers without reducing aperture ratio.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the invention provides a color filter substrate, comprisinga substrate and a plurality of color filters formed on the substrate,wherein at least two adjacent ones of the color filters overlap to forma plurality of patterned regions, an opening in one of the patternedregions, a planarization layer covering the color filters and fillingthe opening, and a transparent conductive layer formed on theplanarization layer.

The invention also provides a liquid crystal display, comprising thecolor filter substrate, an opposite substrate disposed opposite to thecolor filter substrate, a spacer disposed between the color filtersubstrate and the opposite substrate, and a liquid crystal layerdisposed between the color filter substrate and the opposite substrate.

The invention further provides a color filter substrate, comprising asubstrate, a first color filter formed on the substrate, a second colorfilter formed on the substrate, wherein a patterned region is formedbetween the first and second color filters, a planarization layercovering the first and second color filters, and a conductive layer onthe planarization layer.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1A is a top view of a conventional color filter substrate;

FIG. 1B is a section view of line X-X′ in FIG. 1A,

FIGS. 2A-2C, 4A-4C, 5A-5C, 6A-6D, 7A-7C, 8A-8C, and 9A-9C are sectionviews of manufacture of a color filter substrate in an embodiment of theinvention;

FIG. 3 is a top view of a color filter substrate in an embodiment of theinvention; and

FIG. 10 is a section view of a liquid crystal display in an embodimentof the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

FIGS. 2A-2C show a manufacture of a color filter substrate in anembodiment of the invention. First, a red color filter 20R is formed ona substrate 21. The formation may utilize a photoresist containing redpigment spun on the substrate 21. In an embodiment, the substrate 21 canbe plastic, resin, glass, or the like. The color filter 20R is thenpatterned by lithography, for example. As shown in FIG. 2B, a greencolor filter 20G is formed on the substrate 21. The composition and theformation of the color filter 20G are similar to color filter 20R.Similarly, a blue color filter 20B is then formed on the substrate 21 inFIG. 2C. As shown in FIG. 2C, part of the color filter 20G remains oncolor filter 20R to form an overlap region 22A. Similarly, part of thecolor filter 20B remains on the color filter 20G to form an overlapregion 22B. Formation sequence of color filters is not limited to red,green, and blue. Nor are color filters limited to the three conventionalprimary colors, and may include other colors such as cyan, yellow, ormagenta. The overlap regions 22A and 22B can be the same or different.For example, because mixture of green light and blue light is easierthan mixture of green light and red light, the overlap region 22B ispreferably larger than the overlap region 22A to reduce color mixture.Because the aperture ratio of the overlap region 22A and 22B is lessthan the transparent region of the color filters, the overlap regions22A and 22B serve as black matrices, such that the process of formingadditional black matrices may be ignored.

FIG. 3 is a top view of the disclosed structure, and FIG. 2C a sectionview of line Y-Y′ in FIG. 3. In FIG. 2C, the overlap regions 22A and 22Bare formed by left color filters (e.g. 20G or 20B) covering right colorfilters (e.g. 20R or 20G). In another embodiment, it is optional thatright color filters cover left color filters. In further embodiments,outside color filters (e.g. 20R and 20B) can cover middle color filter(e.g. 20G), and vice versa. Color filters 20R, 20G, and 20B have tiltboundary as shown in FIG. 2C, however, their boundary can beperpendicular to the substrate if necessary.

Unlike the conventional technology, when color filters 20R, 20G, and 20Bare patterned, the patterned region 23 is simultaneously formed as shownin FIG. 3. Formation of the patterned region 23 preferably firstcomprises forming a photoresist layer (not shown) on non-patterned colorfilters. The photoresist layer is then patterned by lithography, forexample. Subsequently, the patterned regions 23 of the color filters23R, 23G, and 23B (not masked by the patterned photoresist layer) areremoved. Suitable removal methods comprise dry etching such as reactiveion etching (RIE) or plasma etching. In other embodiments, the patternedregions 23 can be formed by laser ablation, such as direct writing orutilizing a photo mask. FIG. 4A shows a section view of line A-A′ inFIG. 3, wherein patterned regions 23 are lower than the top surface ofthe overlap region 22A. The patterned regions 23 and the top surface ofthe color filters 20R, 20G, 20B are of the same height. In otherembodiments, the patterned regions 23 can be openings in FIG. 4B lowerthan the top surface of the color filters 20R, 20G, and 20B. In furtherembodiments, the patterned regions 23 can expose the substrate 21. FIGS.5A-5C show a section view of line B-B′ in FIG. 3 at about the middle ofthe overlap region 22A. As shown in FIG. 5A, the patterned region 23 andthe color filters 20R are of the same height, such that color filter 20Ris covered by the color filter 20G in the patterned region 23. As shownin FIG. 5B, the patterned region 23 is an opening, and part of the colorfilter 20R is exposed in the patterned region 23. As shown in FIG. 5C,the patterned region 23 exposes part of the substrate 21. The describedpatterned regions 23 and the overlap regions 22A/22B may be of the sameor different widths. Additionally, patterned regions 23 are not formedin all overlap regions 22A and 22B, only being formed in part of theoverlap regions 22A and 22B if necessary. While patterned regions 23 arecircular in FIG. 3, other shapes such as square, rectangle, rhomb,hexagon, or ellipse are possible. The width of the overlap region 22Aand 22B can be the same or different.

A planarization layer 30 is then formed overlying the describedstructure, as shown in FIGS. 6A-6C. FIGS. 6A-6C correspond to line A-A′in FIG. 3. The planarization layer 30 can be transparent material,organic material, or combinations thereof. The openings in FIGS. 4B-4Care filled by the planzarization layer 30 to complete a smooth topsurface. FIG. 6D shows the structure, after formation of theplanarization layer 30, continued from FIG. 2C corresponding to lineY-Y′ in FIG. 3. Overlap regions 22A and 22B have a higher top surfacethan color filters 20R, 20G 20B other than the overlap regions, however,the top surface of the planarization layer 30 can be planarized to beuniformly smooth by back etching. FIGS. 7A-7C show the structure, afterformation of the planarization layer 30, continued from the FIGS. 5A-5Ccorresponding to line B-B′ in FIG. 3. Irrespective of whether or not thepatterned regions 23 are of the same height as shown in FIGS. 4A and 5A,openings as in FIGS. 4B and 5B, or exposed substrate 21 as in FIGS. 4Cand 5C, the planarization layer 30 has a smooth top surface. It isclearly shown in figures that the planarization layer 30 is thickest onpatterned region 30, thinner on color filters 20R, 20G, and 20B, andthinnest (can be zero) on the overlap regions 22A and 22B. In anembodiment, the planarization layer 30 has a thickness of about 0 μm to10 μm, and more preferably of about 0.5 μm to 4 μm.

After formation of a conductive layer 40 on the structure, spacers 50are formed in the patterned region 23. Generally, the conductive layer40 can be indium tin oxide (ITO), indium zinc oxide (IZO), or aluminumzinc oxide (AZO), and have a thickness of about 400 Å to 2000 Å.Suitable spacers 50 include positive or negative photoresist. FIGS.8A-8C continue from FIGS. 6A-6C, and FIGS. 9A-9C continue from FIGS.7A-7C, respectively. Compared to the conventional technology, thepatterned regions 23 of the present embodiments unlike the overlapregions 22A and 22B influenced by the overlap of the color filters 20R,20G, and 20B, such that the spacers 50 formed overlying the patternedregions 23 have uniform height. Especially in FIG. 8C, onlyplanarization layer 30 and conductive layer 40 formed on the exposedsubstrate 21 in the patterned regions 23, the influence from colorfilters 20R, 20G, and 20B to spacers 50 can be totally eliminated. Inaddition, the spacers 50 are not formed in the transparent regions ofthe color filters, thereby retaining the aperture ratio. Note that whilespacers 50 have a rectangular cross section in illustration, they may beladder-shaped with narrow top and wide bottom, conical, or othersuitable shape. FIGS. 8A-8C show two spacers in three color filters, butthe spacer density is not limited thereto. In other words, part of thepatterned regions 23 may be free of spacer 50. If color filters 20R,20G, and 20B are large, dense spacers are needed. If color filters 20R,20G, and 20B are small, it is possible that several sets of colorfilters 20R, 20G and 20B need only one spacer 50. As long as the supportis sufficient, the skilled may optionally tune the spacer 50 factorssuch as density, shape, color, size, material, and number.

Using the color filter substrate in FIG. 8C as example, a liquid layeris disposed between the color filter substrate and an array substrate toform a liquid crystal display. As shown in FIG. 10, the bottom substrateis color filter substrate 90A with description thereof omitted forbrevity. The top substrate is the array substrate 90C. The substrate 25of the array substrate 90C is similar to substrate 21. In themulti-layered structure 27, data lines 60 are preferably wider than thepatterned regions 23 or overlap regions 22A and 22B (please referring toFIG. 10). The liquid crystal layer 90B is disposed between the colorfilter substrate 90A and the array substrate 90C to complete the liquidcrystal display 100 of the present embodiments.

While the invention has been described by way of example and in terms ofpreferred embodiment, it is to be understood that the invention is notlimited thereto. To the contrary, it is intended to cover variousmodifications and similar arrangements (as would be apparent to thoseskilled in the art). Therefore, the scope of the appended claims shouldbe accorded the broadest interpretation so as to encompass all suchmodifications and similar arrangements.

1. A color filter substrate, comprising a substrate; a plurality ofcolor filters formed on the substrate, wherein at least two adjacentones of the color filters overlap to form a plurality of overlap regionsand an opening in one of the overlap regions; a planarization layercovering the color filters and filling the opening; and a transparentconductive layer formed on the planarization layer.
 2. The color filtersubstrate as claimed in claim 1, wherein the color filters have colorscomprising red, green, blue, cyan, yellow, or magenta.
 3. The colorfilter substrate as claimed in claim 1, wherein the overlap regions havethe same area.
 4. The color filter substrate as claimed in claim 1,wherein the opening exposes part of the color filters.
 5. The colorfilter substrate as claimed in claim 1, wherein the opening exposes partof the substrate.
 6. The color filter substrate as claimed in claim 1,wherein the opening is circular, square, rectangular, rhomboid,hexagonal, or elliptical.
 7. The color filter substrate as claimed inclaim 1, wherein one of the overlap regions and the opening havesubstantially the same width.
 8. The color filter substrate as claimedin claim 1, wherein the planarization layer comprises transparentmaterial, organic material, or combinations thereof.
 9. The color filtersubstrate as claimed in claim 1, wherein the overlap regions havedifferent areas.
 10. A liquid crystal display, comprising: a colorfilter substrate as claimed in claim 1; an opposite substrate disposedopposite to the color filter substrate; a spacer disposed between thecolor filter substrate and the opposite substrate; and a liquid crystallayer disposed between the color filter substrate and the oppositesubstrate.
 11. The liquid crystal display as claimed in claim 10,wherein the spacer is formed on the transparent conductive layer andcorresponds to the opening.
 12. The liquid crystal display as claimed inclaim 10, wherein the opposite substrate comprises data lines having awider width than that of the overlap regions.
 13. A color filtersubstrate, comprising: a substrate; a first color filter formed on thesubstrate; a second color filter formed on the substrate, wherein apatterned region is formed between the first and second color filters; aplanarization layer covering the first and second color filters; and aconductive layer on the planarization layer.
 14. The color filtersubstrate as claimed in claim 13, wherein at least part of the first andsecond filters overlap to form an overlap region, and the patternedregion is formed substantially in the overlap region.
 15. The colorfilter substrate as claimed in claim 14, wherein the planarization layerin the overlap region has a thickness of about 0.5 μm to about 4 μm. 16.The color filter substrate as claimed in claim 13, wherein theplanarization layer in the patterned region is thicker than theplanarization layer on the first and second color filters out of thepatterned region.
 17. The color filter substrate as claimed in claim 13,wherein the first and second filters in the patterned region do notcontact.
 18. The color filter substrate as claimed in claim 17, whereinthe planarization layer in the patterned region has a thickness of about0.5 μm to about 4 μm.
 19. The color filter substrate as claimed in claim17, wherein the planarization layer in the patterned region is thickerthan the planarization layer on the first and second color filters outof the patterned region.
 20. The color filter substrate as claimed inclaim 13, wherein the planarization layer is comprised of organicmaterial, transparent layer, or combinations thereof.